The invention relates to polymerizing radiopaque compositions that include cationically active functional groups and radiopacifying fillers.
Fillers are often added to polymer resins to form composites having higher strength values than the polymer resin itself. Dental composites, for example, typically feature high filler loadings on the order of 50% by weight or higher.
Non-radiopacifying fillers such as quartz and silica have been successfully combined with free radically polymerizable components such as acrylates and methacrylates and a free radical initiator to form a useful dental composite following exposure to polymerization conditions. Such fillers also have been successfully used with cationically polymerizable components such as epoxy resins and a cationic initiator to form useful dental composites following cationic-initiated polymerization.
In many instances it is desirable to use a radiopacifying filler to create a radiopaque composite. Such composites are particularly useful in dental applications because the composite is x-ray detectable. Radiopacifying fillers have been successfully combined with free radically polymerizable components and free radical initiators to form dental composites. It would also be desirable to combine radiopacifying fillers with cationic initiators and cationically polymerizable components such as epoxy resins which undergo less shrinkage than acrylates and methacrylates upon polymerization.